I think they messed up here by only running one fan presale, since it made them predict how many tickets each person with a code would actually purchase. They probably underestimated this number (eg. from people tagging along with their friend who got into the presale), so they ended up selling way more than they thought they would. I suspect this because, at one point, I had 16k people in front of me for 1 night at Mercedes-Benz[0], which is a lot given concert capacity is probably around 50k.
With a two-wave presale (or even "verified fan presale only"), you can put out tickets in even smaller waves and continuously evaluate how many you're giving out based on demand and order ticket quantities.
0: while the queue-it frontend was set up to hide any number above 2,000, the API faithfully showed the actual amount of clients ahead of you in line.
This is tough to enforce unless you have a "1/10th extra fee if you don't show up" policy or allow refunds.